The present invention relates to a flat tube for a header-plateless heat exchanger which is employed for an EGR cooler and the like.
Japanese Patent Laid-Open No. 2013-096632 discloses a flat tube used for a header-plateless heat exchanger. The flat tube is configured such that a pair of groove-like plates are fitted opposite to each other and the openings at both ends are expanded in the thickness direction to form an expanded opening.
Linear side wall parts each with U-like cross section perpendicular to the bottom surface are formed on both side walls of the expanded openings of the both plates. Curved wall parts in which the cross sections of both side walls of each plate curve outward are formed at the sections except the expanded openings.
The side wall part of the expanded opening of the inner plate has, at the midpoint in the height direction, a stepped wall part formed with an inward step portion corresponding to the plate thickness. A pair of guide surfaces each curved and folded inward are formed at the leading edges of each stepped wall part. Each leading end of the guide surfaces is formed so as to abut on the base of the side wall part of the outer plate. The guide surface allows easy assembly of the flat tube.